Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatus
Identification of relevant taxonomic and evolutionary units is a recurrent issue in the fossil record, and all the more for ancient fossils devoid of modern equivalents such as conodonts. Extensive morphological variation has often led to the description of numerous species, subspecies or morphotype...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Pensoft Publishers
2022-02-01
|
| Series: | Fossil Record |
| Online Access: | https://fr.pensoft.net/article/80211/download/pdf/ |
| _version_ | 1797329373440770048 |
|---|---|
| author | Catherine Girard Anne-Lise Charruault Thomas Gluck Carlo Corradini Sabrina Renaud |
| author_facet | Catherine Girard Anne-Lise Charruault Thomas Gluck Carlo Corradini Sabrina Renaud |
| author_sort | Catherine Girard |
| collection | DOAJ |
| description | Identification of relevant taxonomic and evolutionary units is a recurrent issue in the fossil record, and all the more for ancient fossils devoid of modern equivalents such as conodonts. Extensive morphological variation has often led to the description of numerous species, subspecies or morphotypes, which may correspond to end-member morphologies reached through ontogeny. The platform elements of the Late Devonian conodont species Icriodus alternatus were characterized by rows of denticles coming into occlusion between opposite elements; each element grew by the incremental addition of lamellae and by the addition of successive triads during ontogeny. During the late Frasnian and the early Famennian, the important morphological variation within this species led to the description of three subspecies. An extensive sample of early Famennian Icriodus alternatus was quantified using 2D biometric measurements and denticle counts on 2D pictures, showing that the subspecies mainly differed in their size range but not in their general morphology. A 3D morphometric analysis was further performed on a subsample to characterize the shape of the ontogenetically older part of the elements. During ontogeny, early valleys between denticles tended to be filled, and the asymmetry between the inner and outer side of the element increased. These ontogenetic trends are responsible for the morphologies formerly described as the subspecies Ic. alt. mawsonae and Ic. alt. helmsi. Slight discrepancies between temporal ranges of the subspecies may be achieved through variations in range of size reached by the elements as a response to environmental changes. Disparity along ontogeny seems to follow an “hourglass model” suggesting a shift from relatively loose developmental constraints to a pattern of growth modulated by functional constraints during occlusion. |
| first_indexed | 2024-03-08T07:04:44Z |
| format | Article |
| id | doaj.art-738a216492224bbebc23235c005e9b4d |
| institution | Directory Open Access Journal |
| issn | 2193-0074 |
| language | English |
| last_indexed | 2024-03-08T07:04:44Z |
| publishDate | 2022-02-01 |
| publisher | Pensoft Publishers |
| record_format | Article |
| series | Fossil Record |
| spelling | doaj.art-738a216492224bbebc23235c005e9b4d2024-02-03T05:04:28ZengPensoft PublishersFossil Record2193-00742022-02-01251254110.3897/fr.25.8021180211Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatusCatherine Girard0Anne-Lise Charruault1Thomas Gluck2Carlo Corradini3Sabrina Renaud4Univ MontpellierUniv MontpellierUniv MontpellierUniversità degli Studi di TriesteUniversité de LyonIdentification of relevant taxonomic and evolutionary units is a recurrent issue in the fossil record, and all the more for ancient fossils devoid of modern equivalents such as conodonts. Extensive morphological variation has often led to the description of numerous species, subspecies or morphotypes, which may correspond to end-member morphologies reached through ontogeny. The platform elements of the Late Devonian conodont species Icriodus alternatus were characterized by rows of denticles coming into occlusion between opposite elements; each element grew by the incremental addition of lamellae and by the addition of successive triads during ontogeny. During the late Frasnian and the early Famennian, the important morphological variation within this species led to the description of three subspecies. An extensive sample of early Famennian Icriodus alternatus was quantified using 2D biometric measurements and denticle counts on 2D pictures, showing that the subspecies mainly differed in their size range but not in their general morphology. A 3D morphometric analysis was further performed on a subsample to characterize the shape of the ontogenetically older part of the elements. During ontogeny, early valleys between denticles tended to be filled, and the asymmetry between the inner and outer side of the element increased. These ontogenetic trends are responsible for the morphologies formerly described as the subspecies Ic. alt. mawsonae and Ic. alt. helmsi. Slight discrepancies between temporal ranges of the subspecies may be achieved through variations in range of size reached by the elements as a response to environmental changes. Disparity along ontogeny seems to follow an “hourglass model” suggesting a shift from relatively loose developmental constraints to a pattern of growth modulated by functional constraints during occlusion.https://fr.pensoft.net/article/80211/download/pdf/ |
| spellingShingle | Catherine Girard Anne-Lise Charruault Thomas Gluck Carlo Corradini Sabrina Renaud Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatus Fossil Record |
| title | Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatus |
| title_full | Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatus |
| title_fullStr | Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatus |
| title_full_unstemmed | Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatus |
| title_short | Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatus |
| title_sort | deciphering the morphological variation and its ontogenetic dynamics in the late devonian conodont icriodus alternatus |
| url | https://fr.pensoft.net/article/80211/download/pdf/ |
| work_keys_str_mv | AT catherinegirard decipheringthemorphologicalvariationanditsontogeneticdynamicsinthelatedevonianconodonticriodusalternatus AT annelisecharruault decipheringthemorphologicalvariationanditsontogeneticdynamicsinthelatedevonianconodonticriodusalternatus AT thomasgluck decipheringthemorphologicalvariationanditsontogeneticdynamicsinthelatedevonianconodonticriodusalternatus AT carlocorradini decipheringthemorphologicalvariationanditsontogeneticdynamicsinthelatedevonianconodonticriodusalternatus AT sabrinarenaud decipheringthemorphologicalvariationanditsontogeneticdynamicsinthelatedevonianconodonticriodusalternatus |